1. Field of the Invention
The present invention is directed to compounds that are substituted 8-phenylquinolines. In particular, this invention is directed to substituted 8-phenylquinolines which are phosphodiesterase-4 inhibitors wherein the phenyl group at the 8-position contains a meta aryl or heterocyclic group.
2. Related Background
Hormones are compounds that variously affect cellular activity. In many respects, hormones act as messengers to trigger specific cellular responses and activities. Many effects produced by hormones, however, are not caused by the singular effect of just the hormone. Instead, the hormone first binds to a receptor, thereby triggering the release of a second compound that goes on to affect the cellular activity. In this scenario, the hormone is known as the first messenger while the second compound is called the second messenger. Cyclic adenosine monophosphate (adenosine 3′,5′-cyclic monophosphate, “cAMP” or “cyclic AMP”) is known as a second messenger for hormones including epinephrine, glucagon, calcitonin, corticotrophin, lipotropin, luteinizing hormone, norepinephrine, parathyroid hormone, thyroid-stimulating hormone, and vasopressin. Thus, cAMP mediates cellular responses to hormones. Cyclic AMP also mediates cellular responses to various neurotransmitters.
Phosphodiesterases (“PDE”) are a family of enzymes that metabolize 3′,5′ cyclic nucleotides to 5′ nucleoside monophosphates, thereby terminating cAMP second messenger activity. A particular phosphodiesterase, phosphodiesterase-4 (“PDE4”, also known as “PDE-IV”), which is a high affinity, cAMP specific, type IV PDE, has generated interest as potential targets for the development of novel anti-asthmatic and anti-inflammatory compounds. PDE4 is known to exist as at lease four isoenzymes, each of which is encoded by a distinct gene. Each of the four known PDE4 gene products is believed to play varying roles in allergic and/or inflammatory responses. Thus, it is believed that inhibition of PDE4, particularly the specific PDE4 isoforms that produce detrimental responses, can beneficially affect allergy and inflammation symptoms. It would be desirable to provide novel compounds and compositions that inhibit PDE4 activity.
A major concern with the use of PDE4 inhibitors is the side effect of emesis which has been observed for several candidate compounds as described in C. Burnouf et al., (“Burnouf”), Ann. Rep. In Med. Chem., 33:91-109(1998). B. Hughes et al., Br. J. Pharmacol., 118:1183-1191(1996); M. J. Perry et al., Cell Biochem. Biophys., 29:113-132(1998); S. B. Christensen et al., J. Med. Chem., 41:821-835(1998); and Burnouf describe the wide variation of the severity of the undesirable side effects exhibited by various compounds. As described in M. D. Houslay et al., Adv. In Pharmacol., 44:225-342(1998) and D. Spina et al., Adv. In Pharmacol., 44:33-89(1998), there is great interest and research of therapeutic PDE4 inhibitors.
International Patent Publication WO9422852 describes quinolines as PDE4 inhibitors. U.S. Pat. No. 6,410,563 describes 8-arylquinoline PDE4 inhibitors.
A. H. Cook, et al., J. Chem. Soc., 413-417(1943) describes gamma-pyridylquinolines. Other quinoline compounds are described in Kei Manabe et al., J. Org. Chem., 58(24):6692-6700(1993); Kei Manabe et al., J. Am. Chem. Soc., 115(12):5324-5325(1993); and Kei Manabe et al., J. Am. Chem Soc., 114(17):6940-6941(1992).
Compounds that include ringed systems are described by various investigators as effective for a variety of therapies and utilities. For example, International Patent Publication No. WO 98/25883 describes ketobenzamides as calpain inhibitors, European Patent Publication No. EP 811610 and U.S. Pat. Nos. 5,679,712, 5,693,672 and 5,747,541 describe substituted benzoylguanidine sodium channel blockers, U.S. Pat. No. 5,736,297 describes ring systems useful as a photosensitive composition.
U.S. Pat. Nos. 5,491,147, 5,608,070, 5,622,977, 5,739,144, 5,776,958, 5,780,477, 5,786,354, 5,798,373, 5,849,770, 5,859,034, 5,866,593, 5,891,896, and International Patent Publication WO 95/35283 describe PDE4 inhibitors that are tri-substituted aryl or heteroaryl phenyl derivatives. U.S. Pat. No. 5,580,888 describes PDE4 inhibitors that are styryl derivatives. U.S. Pat. No. 5,550,137 describes PDE4 inhibitors that are phenylaminocarbonyl derivatives. U.S. Pat. No. 5,340,827 describes PDE4 inhibitors that are phenylcarboxamide compounds. U.S. Pat. No. 5,780,478 describes PDE4 inhibitors that are tetra-substituted phenyl derivatives. International Patent Publication WO 96/00215 describes substituted oxime derivatives useful as PDE4 inhibitors. U.S. Pat. No. 5,633,257 describes PDE4 inhibitors that are cyclo(alkyl and alkenyl)phenyl-alkenyl (aryl and heteroaryl) compounds.
However, there remains a need for novel compounds and compositions that therapeutically inhibit PDE4 with minimal side effects.